The present invention relates to handling systems for conveyed articles having a detectable top and bottom, such as rail tie plates, and more specifically relates to a mechanism for the reorienting of the position of tie plates upon a conveyor surface.
The invention disclosed in the present application is related to the invention disclosed in copending application Ser. No. 203,328, filed June 7, 1988, titled "Method and Apparatus for Automatically Setting Rail Tie Plates", as well as my copending application Ser. No. 203,486, filed June 7, 1988, titled "Automatic Tie Plate Sorting Conveyor".
Tie plates are used to secure rails to railroad ties and comprise a generally flat steel plate with a substantially flat bottom, a plurality of spike holes located on opposite side ends of the plate, and an upper surface having a pair of transverse, parallel, vertically projecting rail-securing ribs or shoulders which define a rail seat therebetween. The tie plate upper surface is slightly angled to provide an inwardly canted rail seat, with more mass of the plate located on the field side thereof to compensate for the force distribution of trains negotiating curves at high speed.
In the process of reconditioning railroad rights-of-way, the existing rail is removed along with the spikes and tie plates, the ties are replaced or resurfaced, and the track bed is refurbished. Before new rails are laid, replacement or recycled tie plates must be accurately positioned upon the ties. Tie plate placement is a cumbersome and labor-intensive operation, due to the significant weight of the individual plates (18-40 lbs. each) and the rapid rate at which they must be positioned to keep up with the other operations of track reconditioning, most of which are largely automated.
Normally a member of a plate handling crew must retrieve steel plates individually from an often tangled pile and properly orient each plate for setting upon the upper surface of a tie to form new track beds. Two hands are required to position each plate due to their size and significant weight. If the plate is inverted, a worker must get his hands under the plate and turn it over. Typically, this is done on the ground or on a steel table surrounded by other plates and track material. Accurate plate placement upon the ties is critical, for the plates are required to be positioned within 1/4 inch on an imaginary x-y plane parallel to the ground. The configuration of the plates is such that the vertically projecting ribs or shoulders must be facing upwardly and the planar bottom below for proper rail placement thereon. It has been estimated that a member of a plate setting crew will handle 150,000 pounds of plates per eight hour shift. In order for the manual plate setting operation to keep up with the other automatic track reconditioning operations of the rail gang for maximum efficiency, the workers must lay plates at the rate of 30 to 40 plates per minute. These conditions create a situation where operator fatigue and safety are major concerns.
Previous attempts at automating the tie plate setting operation resulted in devices largely concerned with the actual placement of the plates upon the ties. These prior art setters depended on a supply of plates which had already been manually oriented either on or off-site. On-site, the plates are often prepositioned upon the shoulder of the track bed, or carried in a gondola to be fed via conveyors to the plate setting device. In conventional plate handling processes, it is common to transfer plates from one location of the rail gang to another using inclined slide conveyors. However, the rapid rate of 30-40 plates per minute at which automatic tie plate setters must operate to keep up with other automated track maintenance equipment requires extensive preplacement and manual handling and sorting of plates.
Also, in commonly assigned U.S. Pat. No. 4,727,989, there is disclosed an automatic tie plate orientation sensing system which is designed to sense the orientation of plates upon a conveyed surface to determine whether or not the plates are inverted. The sensing system is also designed to transmit a signal upon the sensing of an improperly oriented or inverted plate. Consequently, there is a need for a tie plate handling mechanism which automatically inverts improperly oriented plates on a rapid basis and thus minimizes the operator's effort in properly orienting the position of tie plates. Such a mechanism would assist the plate setting operation in keeping up with other automated track repair and reconditioning equipment. Also, if the labor expended by a worker in flipping inverted plates could be alleviated, the operator fatigue factor would be significantly reduced.
Accordingly, the automatic high speed tie plate reorienting mechanism of the invention is designed to be triggered by a separate plate orientation sensing apparatus which determines whether a conveyed tie plate is in either the inverted or the properly oriented position. Once the plate reorienting mechanism is triggered by the plate orientation sensing system, the reorienting mechanism is designed to stop the conveyed travel of the plate and invert or flip the plate to be in proper orientation for placement upon the tie.